Frequency sensors for use in subterranean formation operations

ABSTRACT

The present disclosure relates to vibration frequency sensors comprising a vibratable flow tube having an interior for receiving a fluid, a vibration detector coupled to the flow tube for detecting a frequency of the fluid received by the flow tube during vibration thereof; and measurement circuitry coupled to the vibration detector for determining a frequency shift over time of the detected frequency. At least a portion of a surface of the interior of the flow tube is functionalized with a reactant sensitive to the analyte, and the frequency shift corresponds to the presence of the analyte, the analyte having reacted with the reactant.

BACKGROUND

The embodiments herein relate generally to apparatus and methods for usein subterranean formation operations and, more particularly, tofrequency sensors and methods of use thereof for detecting analytes insubterranean formation operations.

Hydrocarbon fluids, including oil and natural gas, are obtained fromwellbores drilled into subterranean formations (or simply “formations”)having hydrocarbon-rich reservoirs. After the wellbore is drilled, it iscompleted by installation of specially designed equipment and materialsto facilitate and control hydrocarbon production. At any point duringthe design, drilling, and completion of a particular wellbore, it may bedesirable to obtain certain information about the characteristics of theproduced fluids from the formation. As used herein, the term “producedfluids,” and grammatical variants thereof, refers to, any fluidrecovered to the surface from a wellbore that is not an introducedtreatment fluid (i.e., not a fluid that was placed into the wellbore).Accordingly, produced fluids may be oil, gas, water, and the like.

It may be desirable to determine whether deleterious materials (e.g.,corrosive materials, metallurgic reactant materials, and the like). Suchdeleterious materials can affect equipment and/or operators involved inupstream, midstream, and downstream oil and gas sectors. As used herein,the “upstream” sector refers to exploration and production of crudeformation fluids; the “midstream” sector refers to transportation andstorage of crude formation fluids; and the “downstream” sector refers torefinement of crude formation fluids, including processing and purifyingraw natural gas.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain features andinventive aspects of the embodiments described herein, and should not beviewed as exclusive embodiments. The subject matter disclosed is capableof considerable modifications, alterations, combinations, andequivalents in form and function, as will occur to those skilled in theart and having the benefit of this disclosure.

FIG. 1 depicts a cross-sectional view of a frequency sensor, accordingto one or more embodiments of the present disclosure.

FIG. 2 depicts a cross-sectional view of a frequency sensorfunctionalized with two reactants, according to one or more embodimentsof the present disclosure.

FIG. 3 depicts a cross-sectional view of a frequency sensor systemhaving a pair of frequency sensors each having a vibration detectorcommunicably coupled to measurement circuitry, according to one or moreembodiments of the present disclosure.

FIG. 4 is a schematic diagram of an exemplary drilling system that mayemploy the principles of the present disclosure.

FIG. 5 is a schematic diagram of an exemplary wireline system that mayemploy the principles of the present disclosure.

DETAILED DESCRIPTION

The embodiments herein relate generally to apparatus and methods for usein subterranean formation operations and, more particularly, tofrequency sensors and methods of use thereof for detecting analytes insubterranean formation operations. Specifically, the frequency sensorsof the present disclosure synergistically combine a vibratable flow tubehaving a reactant sensitive to an analyte of interest functionalizedthereto. The frequency sensor is able to detect a frequency shiftcorresponding to the presence of the analyte that has reacted with thereactant in real-time or near real-time. The frequency shift canrespond, for example, to the change in mass, or density, of a particularreactant once it has reacted with the analyte. For example, thefrequency shift to increased mass of the reactant (e.g., by absorptionof an analyte) drives a decrease in frequency, and vice versa. Aspreviously mentioned, the frequency sensors described herein may beemployed at any point during the design, drilling, and completion of aparticular wellbore to obtain information about a particular analyte.

The embodiments herein employ frequency sensors for detection of ananalyte of interest within a formation fluid, including deleteriousmaterial analytes, which are of particular interest. As used herein, theterm “fluid” refers to liquid phase and gaseous phase substances. Asused herein, the term “analyte,” and grammatical variants thereof,refers to a material (or substance) whose chemical and/or physicalattributes are being qualitatively and/or qualitatively detected.Although the embodiments described herein are described with referenceto detecting potentially deleterious analytes, it is to be appreciatedthat non-deleterious analytes may also be detected and/or measured inaccordance with the embodiments of the present disclosure.

The frequency sensors described herein may be used in upstream,midstream, or downstream processes and/or equipment, without departingfrom the scope of the present disclosure. For example, the frequencysensor(s) may be employed in a downhole formation testing tool within awellbore that collects, monitors, analyzes, and/or brings formationfluid samples to surface. Such formation testing tools are sealed toolsthat typically contain a passage or flow channel that is used towithdraw fluid directly from the formation. The formation fluid iscollected within the tool and analyzed in the wellbore using thefrequency sensors described herein, and can additionally be brought tothe surface for duplicate or further analysis, which may or may notemploy the frequency sensors described herein. The frequency sensor maybe located within a formation testing tool in an oil fluid stream, a gasfluid stream, and/or an aqueous fluid stream at a downhole location(e.g., a hydrocarbon producing wellbore, a mining operation, a remedialcontaminated groundwater operation, and the like). In some embodiments,the formation testing tool may be part of a wireline system used duringa drilling application, for example, for conveying the data receivedfrom the frequency sensor to the surface for monitoring. Such wirelinesystems are described in greater detail below. The frequency sensors mayfurther be employed in transport and storage equipment (e.g., apipeline, a truck, a rail car, an oil tanker, a barge) for conveying theformation fluid to one or more locations or for maintaining it at aparticular location, and in which the formation fluid comes intocontact. Additionally, the frequency sensors may be utilized inprocessing, refining, and purifying equipment that contacts theformation fluid. Accordingly, the frequency sensors may be located in anoil fluid stream or a gas fluid stream at one or more surface locations,such as a fluid stream forming part of a chemical plant.

In some embodiments, the frequency sensor may be used at one or morelocations during any or all of upstream, midstream, and downstreamsector operations or processes. In such a manner, for example, one ormore desired analytes can be monitored throughout all or a portion of aformation fluids lifetime prior to delivery to an end-user. Moreover,interactions with specific equipment can be pinpointed or otherwiseelucidated that result in increasing or decreasing levels of one or moredesired analytes.

As previously mentioned, deleterious analytes may be particularlydesirable to detect in formation fluids. For example, mercury present information fluid (e.g., in a gaseous stream from a formation, such as apipeline, storage equipment, or processing equipment) can result inmetallurgical equipment failures (e.g., heat exchange equipment) due toamalgamation of the equipment surfaces with the mercury in the formationfluid. Such amalgamation may cause equipment failure or reduce theefficacy or efficiency of the equipment. Indeed, in some instances,formation fluids can produce upwards of 500 grams (g) of elementalmercury per day (e.g., gas fields in Malaysia, Thailand, and Australia),which can significantly affect equipment, operations, and costs. Asanother example, hydrogen sulfide (H₂S) present in formation fluid canresult in environmental, health, and safety concerns. Hydrogen sulfideis extremely poisonous, corrosive, flammable, and explosive. It cancause stress corrosion cracking when combined with water, resulting inmicro-cracks in metal equipment that reduces the metals tensile stress(and thus the stress at which it may fail). Other analytes of interestinclude, but are not limited to, a salt, carbon dioxide, solidparticulates, and any combination thereof, as discussed in greaterdetail below.

One or more illustrative embodiments disclosed herein are presentedbelow. Not all features of an actual implementation are described orshown in this application for the sake of clarity. It is understood thatin the development of an actual embodiment incorporating the embodimentsdisclosed herein, numerous implementation-specific decisions must bemade to achieve the developer's goals, such as compliance withsystem-related, lithology-related, business-related, government-related,and other constraints, which vary by implementation and from time totime. While a developer's efforts might be complex and time-consuming,such efforts would be, nevertheless, a routine undertaking for those ofordinary skill in the art having benefit of this disclosure.

It should be noted that when “about” is provided herein at the beginningof a numerical list, the term modifies each number of the numericallist. In some numerical listings of ranges, some lower limits listed maybe greater than some upper limits listed. One skilled in the art willrecognize that the selected subset will require the selection of anupper limit in excess of the selected lower limit. Unless otherwiseindicated, all numbers expressing quantities of ingredients, propertiessuch as molecular weight, reaction conditions, and so forth used in thepresent specification and associated claims are to be understood asbeing modified in all instances by the term “about.” As used herein, theterm “about” encompasses +/−5% of a numerical value. For example, if thenumerical value is “about 80%,” then it can be 80%+/−5%, equivalent to76% to 84%. Accordingly, unless indicated to the contrary, the numericalparameters set forth in the following specification and attached claimsare approximations that may vary depending upon the desired propertiessought to be obtained by the exemplary embodiments described herein. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claim, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsand steps. When “comprising” is used in a claim, it is open-ended.

As used herein, the term “substantially” means largely, but notnecessarily wholly.

The use of directional terms such as above, below, upper, lower, upward,downward, left, right, uphole, downhole and the like are used inrelation to the illustrative embodiments as they are depicted in thefigures, the upward direction being toward the top of the correspondingfigure and the downward direction being toward the bottom of thecorresponding figure, the uphole direction being toward the surface ofthe well and the downhole direction being toward the toe of the well.

Referring now to FIG. 1, illustrated is a cross-sectional view of afrequency sensor, according to one or more embodiments of the presentdisclosure. As shown, frequency sensor 100 comprises a vibratable flowtube 102 (or simply “flow tube 102”) having an interior 104. Theinterior 104 defines flow bore 106 through which fluid can flow(arrows). Although the flow tube 102 is shown as having a horizontal (orstraight) configuration, it is to be appreciated that otherconfigurations for the flow tube 102 may be utilized in accordance withthe embodiments described herein (e.g., vertical, deviated (slanted),S-shaped, C-shaped, U-shaped, D-shaped spiral-shaped, and the like),without departing from the scope of the present disclosure. Selection ofthe particular configuration of the flow tube 102 will depend on anumber of factors including, but not limited to, the direction of fluidflow, the location in which the frequency sensor 100 is placed (e.g.,downhole, a pipeline, and the like), and the like, and any combinationthereof. Preferred shapes for theoretical modeling and datainterpretation may include horizontal (or straight) configurations andU-shaped configurations. The flow tube 102 may be encased or otherwisesupported by a housing 108 that can be made of a rigid material that notonly provides support to the flow tube 102, but also aids in isolating avibrating region 110. In some embodiments, as shown, an annular area isformed in the vibrating region 110 between the flow tube 102 and thehousing 108.

Within the vibrating region 110, at least a portion of the interior 104of the flow tube 102 is functionalized with a reactant 112 sensitive toan analyte of interest in a fluid (e.g., a formation fluid) fordetection based on a frequency shift by the frequency sensor 100, asdescribed below. As used herein, the term “at least a portion” withreference to functionalization of the interior 104 of the flow tube 102with a reactant 112 refers to at least about 0.1% of the surface of theinterior 104 in the vibrating region 110 being functionalized with thereactant 112. That is, at least about 0.1% of the interior 104 of theflow tube 102 is functionalized with reactant 112, up to (as shown) 100%of the interior 104 of the flow tube 102 is functionalized with reactant112. The portion of the vibrating region 110 being functionalized withthe reactant 112 may be determined based on the desired targetsensitivity and longevity of the sensor, taking into account resolutionin frequency measurement, the mass change in reactant and analyteinteraction, and the like.

Referring now to FIG. 2, with continued reference to FIG. 1, illustratedis frequency sensor 200, which is substantially similar to frequencysensor 100 of FIG. 1, except that two reactants 112 a, 112 b arefunctionalized onto the interior 104 of flow tube 102. Accordingly, eachof the two reactants 112 a, 112 b are sensitive to a different analyteand the frequency sensor 200 detects two frequency shifts associatedwith each of the two reactants 112 a,b, and the measurement circuitry120 determines frequency shifts corresponding to each single analyte, asdescribed below. It is to be appreciated that although FIG. 2 depictstwo reactants 112 a, 112 b, a plurality (two or more) of reactants maybe functionalized onto the interior 104 of the flow tube 102, withoutdeparting from the scope of the present disclosure. Moreover, theplurality of reactants may be functionalized onto the interior 104 ofthe flow tube 102 in any configurations, including a spaced-apartconfiguration (as shown) or a random configuration, and the amount ofany one reactant may be more, less, or the same in amount compared toany other reactant. The configuration and amount of any particularreactant will depend on, at least in part, the particular type andamount of analytes expected to be encountered in a particular fluid(e.g., formation fluid).

It is to be appreciated that the frequency shift sensitivity may becompromised where a plurality of reactants are used with a singlefrequency sensor, and reactants expected to have very differentfrequency shifts may be preferable. In some embodiments, the frequencyshift measurement together with measurement of the mode shape ofvibration can be used to differentiate reactants, or a very thin-massedflow tube material is used (e.g., graphene, carbon nanotubes, and thelike), to enhance sensitivity where a plurality of reactants are used ina single frequency sensor. The reactive area within the flow tube can beused to accentuate a mode shape and a sensitivity to an analyte. Inother embodiments, the sensitivity can be enhanced by coating each ofthe different reactants at known portions of the flow tube 102 in thevibrating region 110 to depress and enhance various features of thefrequency spectra. For example, if the reactant 112 a can be coated at a¼ portion of the flow tube 102 and a ⅓ portion of the flow tube 102 inthe vibrating region and the reactant 112 b at known portions adjacentthereto or therebetween.

Referring back to FIG. 1, the flow tube 102 is composed of any materialcapable of vibrating and capable of having a reactant 112 functionalizedthereto. In some embodiments, the flow tube 102 is composed of aplastic, a metal, a ceramic, a glass, and any combination thereof. Thatis, the flow tube 102 may be composed of a composite material of two ormore of a plastic, a metal, or a ceramic. In such instances, theproperties of the individual materials retain their specificcharacteristics, but can be used to synergistically enhance theproperties of the flow tube 102, such as by enhancing functionalizationof the reactant 112 thereon. For example, the flow tube 102 may be acomposite material of ceramic fibers embedded in a metal or polymermatrix. In some specific embodiments, for example, the flow tube 102 iscomposed of graphene, carbon nanotubes, fiber glass, graphite, agraphite composite, a carbon-fiber reinforced polymer, polyether etherketone, an organic polymer, epoxy, ceramic (e.g., aluminum oxide, anitrogen doped aluminum oxide, and the like), and any combinationthereof. In some embodiments, the flow tube 102 is one of fiber glass,graphite, a graphite composite, a carbon-fiber reinforced polymer,polyether ether ketone, an organic polymer, epoxy, ceramic, and anycombination thereof coated with graphene, carbon nanotubes, and anycombination thereof. The selection of the particular type of materialfor forming the flow tube 102 depends, at least in part, on the analyteof interest to be detected, the reactant 112 to be functionalizedthereto, the functionalization method selected, and the like, and anycombination thereof.

The reactant 112 selected to be functionalized on the interior 104 ofthe flow tube 102 is selected based on the analyte of interest in thefluid to be examined, where the reactant 112 reacts with the analyte insome manner. For example, the analyte may react with the reactant 112 bydegrading (or dissolving) the reactant 112, by absorbing the analyte tothe reactant 112, by wearing away (or eroding) the reactant 112, and thelike. Analytes of interest may be any compound or particulate present ina fluid (e.g., a formation fluid) of interest. For example, the analytemay be a corrosive compound, a gas of interest (e.g., carbon dioxideconsidered a greenhouse gas whose identification and capture may bedesirable), a compound signifying a process failure (e.g., particulateerosion of the reactant 112 signifying a screen break), and the like.Examples of suitable analytes include, but are not limited to, hydrogensulfide, mercury, salt, carbon dioxide, solid particulates, biologicalmolecules, microorganisms, and any combination thereof.

Examples of reactants 112 that can be functionalized on the interior 104of the flow tube 102 that are sensitive to analytes in a fluid include,but are not limited to, gold, silver, copper, iron, nickel, a goldalloy, a silver alloy, a copper alloy, an iron alloy, a nickel alloy, aprecious metal, a noble metal, a precious metal alloy, a noble metalalloy, a solid chelating agent, sulfur-limonene polysulfide, apiezoelectric crystal, a salt, a frangible material, an antibody, andany combination thereof. As used herein, the term “alloy” is a metalmade by combining two or more metallic elements, where at least 50% ofthe alloy comprises the named metal (e.g., a gold alloy comprises atleast 50% gold). As examples of reactant-analyte pairings, gold, goldalloys, precious metals (e.g., gold, silver, platinum, palladium,ruthenium, rhodium, osmium, iridium), sulfur-limonene polysulfide, andpiezoelectric crystals are sensitive to mercury; and frangible materialsare sensitive to solid particulates; noble metals (e.g., ruthenium,rhodium, palladium, silver, osmium, iridium, platinum, gold, mercury,rhenium) alloyed with iron are sensitive to hydrogen sulfide; antibodiesare sensitive to biological molecules and microorganisms.

The reactants 112 described herein are functionalized to the interior104 of the flow tube 102 by any means suitable for the two materials.Specific examples of functionalization methods include, but are notlimited to, adhering the reactant 112 to the interior 104 (e.g., with anadhesive such as a resin, a tackifying agent, a glue, and the like),mechanically attaching the reactant 112 to the interior 104 (e.g., witha mechanical fastener such as a clamp, a latch, a spring connection, acrew, a bolt, a nail, and the like), brazing the reactant 112 to theinterior 104 (e.g., by soldering with a metal or alloy, such as acopper-zinc alloy, at high temperature), welding the reactant 112 to theinterior 104 (e.g., joining together by heating the surfaces to amelting point), chemical deposition of the reactant 112 to the interior104, and any combination thereof. The chemical deposition of thereactant 112 to the interior 104 may be by any means compatible with thereactant 112 and the material forming the interior 104 of the flow tube102 to permit functionalization. Specific examples of chemicaldeposition methods include, but are not limited to, nickel plating,electrodeless nickel plating, electroplating, chemical vapor deposition,atomic layer deposition, precipitation, and the like, and anycombination thereof.

In some embodiments, as shown, the measurements may be taken as fluidflows through the flow tube 102 in the vibrating region 110. In otherembodiments, the housing may be configured to completely isolate aportion of fluid within the flow tube 102 in the vibrating region 110 toobtain measurements for a particular period of time. For example, thehousing 108 can be equipped with end bulkheads that are capable offorming a dividing wall or barrier to retain a portion of fluid withinthe vibrating region 110, which is later released (e.g., a sliding doormechanism, a swinging door mechanism, a valve, and the like), withoutdeparting from the scope of the present disclosure.

The frequency sensor 100 detects the analyte by a frequency shift formedfrom reacting with the reactant 112. To this end, in some embodiments,the frequency sensor 100 includes a vibration source 114, a vibrationdetector 116, and measurement circuitry 120. The vibration source 114 iscoupled to the flow tube and configured to excite vibration of the flowtube 102 in the vibrating region 110. As used herein, the term“coupled,” and grammatical variants thereof, includes both an indirector direct connection. In certain embodiments, the vibration source 114may be an electromagnetic hammer used to strike the flow tube 102 in thevibrating region 110, a magnetic field (e.g., where the flow tube 102 isplaced within the magnetic field and alternative currents passtherethrough), a mechanical shaker, an acoustic frequency generator, andany combination thereof.

The frequency sensor 100 comprises a vibration detector 116 coupled tothe flow tube 102 in the vibrating region 110. The vibration detector116 detects at least one frequency at a specific time or over time of afluid in the flow tube 102 in the vibrating region 110. The vibrationdetector 116 may be any device or object capable of detecting frequencyand capable of being communicably coupled to measurement circuitry 120,which is able to analyze the detected frequencies from the vibrationdetector 116, such as frequency shifts associated with the reaction ofthe analyte and the reactant 112. Examples of suitable vibrationdetectors include, but are not limited to, a metallic wire, a fiberoptic (e.g., an optical sensor), a strain gauge, an accelerometer, apiezoelectric sensor, a magnet-voice coil, a displacement sensor, andany combination thereof. As examples, if the vibration detector 116 is afiber optic, the vibration detected can be light reflected off thevibrating flow tube 102 in response to the analyte and reactant 112reacting; if the vibration detector 116 is an accelerometer, thevibration detected can be acceleration or deceleration of the vibratingflow tube 102 in response to the analyte and reactant 112 reacting; ofif the vibration detector 116 is a displacement sensor, the vibrationdetected can be sound generated by the vibrating fluid tube 102 inresponse to the analyte and reactant 112 reacting.

Although the location of the vibration source 114 in FIG. 1 (and FIG. 2)is upstream of the vibration detector 116, it is to be appreciated thatthe vibration source 114 (when integral to the frequency sensor 100) andthe vibration detector 116 may be in any configuration relative to eachother, provided that the vibration source 114 is able to excitevibration of the flow tube 102 in the vibrating region 110 and thevibration detector 116 is able to detect vibration frequency in thevibrating region 110, without departing from the scope of the presentdisclosure.

The vibration detector 116 is communicably coupled to measurementcircuitry 120 via communication line 118. As shown, the measurementcircuitry 120 is integral to the housing 108; however, it is to beappreciated that the measurement circuitry 120 may be communicablycoupled to the vibration detector 116 via communication line 118 withoutthe measurement circuitry 120 being integral to the frequency sensor 100(including the housing 108), such as where the measurement circuitry isa separate component that connects to the frequency sensor 100 via thecommunication line 118, without departing from the scope of the presentdisclosure. The communication line 118 is an electrical connection,which may be wired or wireless, which permits communication between thevibration detector 116 and the measurement circuitry 120 such that themeasurement circuitry 120 can analyze the frequencies detected by thevibration detector 116. The measurement circuitry 120 determines atleast a frequency shift corresponding to the presence of the analyte dueto the reaction of the analyte with the reactant 112. That is, thevibrating flow tube 102 having the reactant 112 functionalized thereonand unreacted has a particular frequency, wherein the reaction of thereactant 112 with the analyte in a fluid in the flow tube 102 results ina different frequency, which may be either greater or lesser than theunreacted frequency. The measurement circuitry 120 measures thisfrequency shift, and such frequency shift corresponds to one or more ofa characteristic of the analyte including, but not limited to, a mass ofthe analyte, a concentration of the analyte, a diffusion coefficient ofthe analyte, and any combination thereof.

As an example, the measurement circuitry 120 may include a spectralanalyzer configured to perform a specific transform on the frequencies(which may be time-based) received by the vibration detector 116. Insome embodiments, the measurement circuitry 120 may include a processordesigned to execute instructions stored in memory coupled to theprocessor to perform the transform functions and then later to determinethe desired frequency shift associated with the presence of the analyte.

In some instances, the measurement circuitry 120 can be used to measurea frequency shift corresponding to the concentration of the analyte andbased on the initial density of the functionalized reactant 112, thefinal density of the functionalized reactant 112 based on the frequencyshift (i.e., after reacting with the analyte). As another example, themeasurement circuitry 120 can be used to measure a frequency shiftcorresponding to the diffusion coefficient of the analyte, where theconcentration of the analyte is known by manipulating flow rate (e.g.,by ceasing flow rate using bulkheads) in the flow tube 102, where theincrease or decrease in the density of the reactant 112 correlates tothe diffusion coefficient. In some examples, diffusion coefficient maycorrelate with the rate at which the frequency shift occurs, and byestablishing such correlations, the measurement circuitry 120 can becalibrated for diffusion coefficient measurements. Further, in gases,molecular weight of the gas may be determined; and in liquids, areadimension of the liquid may be determined.

In another embodiment, two or more frequency sensors 100 are used intandem to detect a comparative frequency shift between the two sensors.Referring now to FIG. 3, with continued reference to FIG. 1, illustratedis a frequency sensor system 300 having a pair of frequency sensors eachhaving a vibration detector 116 (FIG. 1) communicably coupled to singlemeasurement circuitry 120 via communication lines 118 a, 118 b eachassociated with a different frequency sensor. Accordingly, thefrequencies detected from both of the frequency sensors can be comparedto obtain a comparative frequency shift by the measurement circuitry120. As used herein, the term “comparative frequency shift” refers to afrequency shift calculated between at least two frequency sensors. Inthis manner, one or more analytes in a fluid may be detected andanalyzed at various points along one or more flow lines or throughoutthe lifetime of a fluid prior to it being conveyed to an end user (e.g.,by wireless communication or wired communication). As one example, afirst frequency sensor can be functionalized with a reactant, whereasthe second frequency sensor is not functionalized and a comparativefrequency shift determined between the two sensors for a particularanalyte, or vice versa.

It is to be appreciated that although single measurement circuitry 120is shown in FIG. 3, each of the individual frequency sensors maycomprise individual measurement circuitry that conveys frequency shiftsto a separate location for analysis, without departing from the scope ofthe present disclosure.

For example, in some embodiments, a first frequency is detected using afirst frequency sensor and a second frequency is detected using a secondfrequency sensor. The vibration detectors of each of the first frequencysensor and the second frequency sensor communicate to single measurementcircuitry via individual communication lines, where the measurementcircuitry determines a comparative frequency shift over time between thefirst frequency and the second frequency, which corresponds to thepresent of an analyte having reacted with a reactant. In some instances,as described above, a plurality of reactants are functionalized to theinterior of the first and/or second frequency sensor flow tubes, and themeasurement circuitry determines frequency shifts corresponding to asingle analyte. In some instances, the plurality of reactants isfunctionalized on a flow tube and a single frequency is detected. Inother instances, a plurality of frequency sensors are functionalized onflow tubes having at least one different reactant between the sensorsand a combined frequency shift is detected by the vibration detector,and the measurement circuitry is able to parse each frequency shiftassociated with each particular analyte/reactant pair. In otherembodiments, only one of the two frequency sensors has a reactantfunctionalized to the interior of the flow tube. In yet otherembodiments, the two frequency sensors have two different reactantsfunctionalized to the interior of the respective flow tubes.

The vibration detector and measurement circuitry described hereindetermines frequency shifts related to reaction between a reactant andan analyte using a frequency sensor. Based on the frequency shift, thepresence of the analyte is determined, as well as one or morecharacteristics about the analyte. In other embodiments, such presenceand characteristics can be determined based on the reverse, where ananalyte that has reacted with the reactant is un-reacted and thefrequencies associated with the un-reaction are detected by thevibration detector and the frequency shift determined using themeasurement circuitry. For example, where the analyte absorbs onto orinto the reactant, thus increasing the mass of the reactant, it can bedesorbed (e.g., by heating, and the like) and the decrease in the massof the reactant is detected as a frequency by the vibration detector,and the frequency shift detected by the measurement circuitry.

As one specific example, the frequency sensor described herein may befunctionalized with a reactant sensitive to mercury. As mentionedpreviously, mercury is a deleterious analyte that will amalgamate withall metal with the exception of iron, although some temperature andpressure may be required for some metals to initiate or accelerate theamalgamation. When mercury is selected as the chosen analyte, as withany analyte, the ideal reactant would be sensitive to mercury over awide range of temperature and pressure, and be sensitive only tomercury. The sensitivity of the reactant is thus driven by the maximumavailable analyte, in this case mercury.

In this example, the frequency sensor is thus configured to detect amercury analyte and the reactant functionalized to the interior of theflow tube of the frequency sensor is gold (e.g., gold film). In thepresence of a mercury analyte, the gold reactant would absorb themercury, thus increasing the mass or density of the gold reactant andlowering the frequency detected by the vibration detector. Additionally,alloying gold with small amounts of metallic sodium will make theamalgamation process of mercury occur both quicker and in the presenceof a water film. Over the duration of a downhole operation, then, theamount of mercury present in a formation fluid could be detected usingthe frequency sensors of the present disclosure by determining theamount of decreased frequency over time. Similarly, as previouslydiscussed, a first frequency sensor may be used that is functionalizedwith a gold reactant and a second frequency sensor may be used in tandemthat is not functionalized with a reactant, where the comparativefrequency shift between the two frequency sensors indicates theaccumulation of mercury (associated with a lower frequency shift and anincrease in mass of the gold reactant on the first sensor). The mercurymay further be dissociated with the gold reactant, such as by heatingthe frequency sensor, where the mercury leaves the amalgam and enters agas phase. If the two sensor system were used as described above, bothfrequency sensors could be headed and the mass loss from the goldreactant will be apparent in the comparative frequency shift, and themass of the mercury could be determined in this manner.

As another specific example, a piezoelectric crystal reactant can beused to detect a mercury analyte. A frequency sensor utilizing apiezoelectric crystal reactant can measure frequency shift using themeasurement circuitry based on quartz crystal microbalance (QCM), whichis a measurement in a mass variation per unit area by measuring thechange in frequency of a quartz crystal resonator (e.g., a piezoelectriccrystal). An advantage of QCM is inherently higher frequencies, whichtranslates into shorter counting or measurement times and highersensitivity and statistical data. Additionally, the smaller mass sensingtarget (i.e., the piezoelectric crystal reactant) is easier to heat topermit desorption of the mercury analyte, and making the frequencysensor itself more compact.

The sensitivity of QCM based on a frequency shift (a change inoscillation frequency) of a piezoelectric crystal with a reactant havinga mass functionalized thereon or thereto can be determined by Equation1, also known as the Sauerbrey equation:

$\begin{matrix}{{{\Delta\; f} = {{- \frac{2\; f_{0}^{2}}{A\sqrt{\rho_{q}\mu_{q}}}}\Delta}},} & {{Equation}\mspace{14mu} 1}\end{matrix}$where f₀ is resonant frequency (unit: Hz), Δf is frequency change(units: Hz), Δm is mass change (unit: g), A is piesoelectrically activecrystal area (the area between electrodes) (unit: cm²), ρ_(q) is densityof the quartz and equal to 2.648 g/cm³), and μ_(q) is the shear modulusof quartz for AT-cut crystal equivalent to 2.947×10¹¹ g·cm⁻¹·s⁻².Parameters such as volumetric and equilibrium time are parametersdetermined during measurement using the frequency sensors describedherein, and are dependent on mercury concentration and pump out volumefrom the flow tube.

The QCM is particularly sensitive for frequency shifts (Δf) of 2% orless, corresponding to a mass change of 2.21×10⁻¹⁵ grams, assuming aresonant frequency (f₀) of 10 MHz. Such sensitivity is adequate fortypical mercury concentrations present in formation fluids, for example.

Equation 1 above relates to frequency shift in a gas (e.g., air). Thefrequency shift in the presence of a liquid (e.g., water or otherNewtonian fluid) can be determined by Equation 2:Δf=−f ₀ ^(3/2)(η_(l)ρ_(l)/ρ_(q)μ_(q))^(1/2)  Equation 2,where η_(l) is the viscosity of the liquid and ρ_(l) is the density ofthe liquid. Corrections may be required to compensate for the densityand viscosity of a liquid fluid, which may be done, for example, byusing the two frequency sensor described above, where one has one typeof QCM and the other a different type with a different resonance, or oneis a QCM and the other is not.

FIG. 4 is a schematic diagram of an exemplary drilling system 400 thatmay employ the principles of the present disclosure, according to one ormore embodiments. As illustrated, the drilling system 400 may include adrilling platform 402 positioned at the Earth's surface and a wellbore404 that extends from the drilling platform 402 into one or moresubterranean formations 406. In other embodiments, such as in anoffshore or subsea drilling operation, a volume of water may separatethe drilling platform 402 and the wellbore 404.

The drilling system 400 may include a derrick 408 supported by thedrilling platform 402 and having a traveling block 410 for raising andlowering a drill string 412. A kelly 414 may support the drill string412 as it is lowered through a rotary table 416. A drill bit 418 may becoupled to the drill string 412 and driven by a downhole motor and/or byrotation of the drill string 412 by the rotary table 416. As the drillbit 418 rotates, it creates the wellbore 404, which penetrates thesubterranean formations 406. A pump 420 may circulate drilling fluidthrough a feed pipe 422 and the kelly 414, downhole through the interiorof drill string 412, through orifices in the drill bit 418, back to thesurface via the annulus defined around drill string 412, and into aretention pit 424. The drilling fluid cools the drill bit 418 duringoperation and transports cuttings from the wellbore 404 into theretention pit 424.

The drilling system 400 may further include a bottom hole assembly (BHA)coupled to the drill string 412 near the drill bit 418. The BHA maycomprise various downhole measurement tools such as, but not limited to,measurement-while-drilling (MWD) and logging-while-drilling (LWD) tools,which may be configured to take downhole measurements of drillingconditions. The MWD and LWD tools may include at least one frequencysensor 426 for determining the presence of an analyte, as describedherein.

As the drill bit 418 extends the wellbore 404 through the formation 406,the frequency sensor 426 may collect data related to formation fluids orproduced fluids related to the presence of a particular analyte. Thefrequency sensor 426 and other sensors of the MWD and LWD tools may becommunicably coupled to a telemetry module 428 used to transfermeasurements and signals from the BHA to a surface receiver (not shown)and/or to receive commands from the surface receiver. The telemetrymodule 428 may encompass any known means of downhole communicationincluding, but not limited to, a mud pulse telemetry system, an acoustictelemetry system, a wired communications system, a wirelesscommunications system, or any combination thereof. In some embodiments,the telemetry module 428 may be omitted and the drill string 412 mayinstead comprise wired drill pipe or wired coiled tubing used totransfer data via wired conductors to a surface receiver. In certainembodiments, some or all of the measurements taken by the frequencysensor 426 may be stored within the frequency sensor 426 or thetelemetry module 428 for later retrieval at the surface upon retractingthe drill string 412.

At various times during the drilling process, the drill string 412 maybe removed from the wellbore 404, as shown in FIG. 5, to conductmeasurement/logging operations. More particularly, FIG. 5 depicts aschematic diagram of an exemplary wireline system 500 that may employthe principles of the present disclosure, according to one or moreembodiments. Like numerals used in FIGS. 4 and 5 refer to the samecomponents or elements and, therefore, may not be described again indetail. As illustrated, the wireline system 500 may include a wirelineinstrument sonde 502 that may be suspended into the wellbore 404 by acable 504. The wireline instrument sonde 502 may include the frequencysensor 426, which may be communicably coupled to the cable 504. Thecable 504 may include conductors for transporting power to the wirelineinstrument sonde 502 and also facilitate communication between thesurface and the wireline instrument sonde 502. A logging facility 506,shown in FIG. 5 as a truck, may collect measurements from the frequencysensor 426, and may include computing facilities 508 for controlling,processing, storing, and/or visualizing the measurements gathered by thefrequency sensor 426. The computing facilities 508 may be communicablycoupled to the frequency sensor 426 by way of the cable 504.

It should also be noted that the various drawings provided herein arenot necessarily drawn to scale nor are they, strictly speaking, depictedas optically correct as understood by those skilled inspectroelectrochemistry. Instead, the drawings are merely illustrativein nature and used generally herein in order to supplement understandingof the systems and methods provided herein. Indeed, while the drawingsmay not be optically accurate, the conceptual interpretations depictedtherein accurately reflect the exemplary nature of the variousembodiments disclosed.

Aspects and examples disclosed herein include:

Embodiment/Example A

A frequency sensor comprising: a vibratable flow tube having an interiorfor receiving a fluid, wherein at least a portion of a surface of theinterior is functionalized with a reactant sensitive to an analyte; avibration detector coupled to the flow tube for detecting a frequency ofthe fluid received by the flow tube during vibration thereof; andmeasurement circuitry coupled to the vibration detector for determininga frequency shift over time of the detected frequency, wherein thefrequency shift corresponds to the presence of the analyte, the analytehaving reacted with the reactant.

Embodiment/Example A may have one or more of the following additionalelements in any combination:

Element A1: Wherein the flow tube is vibratable by a vibration sourcecoupled to the flow tube.

Element A2: Wherein the surface of the interior is functionalized with aplurality of reactants sensitive to a plurality of analytes, and aplurality of frequency shifts is determined where each frequency shiftcorresponds to a single analyte.

Element A3: Wherein the reactant is selected from the group consistingof gold, silver, copper, iron, nickel, a gold alloy, a silver alloy, acopper alloy, an iron alloy, a nickel alloy, a precious metal, a noblemetal, a precious metal alloy, a noble metal alloy, a solid chelatingagent, sulfur-limonene polysulfide, a piezoelectric crystal, a salt, afrangible material, an antibody, and any combination thereof.

Element A4: Wherein the functionalization of the surface of the interiorwith the reactant is selected from the group consisting of adhering thereactant to the surface of the interior, mechanically attaching thereactant to the surface of the interior, chemical deposition to thesurface of the interior, welding the reactant to the surface of theinterior, brazing the reactant to the surface of the interior, and anycombination thereof.

Element A5: Wherein the analyte is selected from the group consisting ofmercury, hydrogen sulfide, a salt, carbon dioxide, solid particulates,biological molecules, microorganisms, and any combination thereof.

Element A6: Wherein the vibration detector is selected from the groupconsisting of a metallic wire, a fiber optic, a strain gauge, and anycombination thereof.

Element A7: Wherein the frequency shift further corresponds to acharacteristic of the analyte, the characteristic selected from thegroup consisting of a mass of the analyte, a concentration of theanalyte, and any combination thereof.

Element A8: Wherein the sensor is located in a formation testing tool.

Element A9: Wherein the sensor is located in an oil fluid stream, a gasfluid stream, or an aqueous fluid stream at a surface location.

Element A10: Wherein the sensor is located in an oil fluid stream, a gasfluid stream, or an aqueous fluid stream at a downhole location in awellbore.

By way of non-limiting example, exemplary combinations applicable to Ainclude: A1-A10; A2, A4, and A8; A9 and A10; A1, A2, A5, and A7; A3 andA6; A7, A8, and A9; and any other combination of any one or more ofA1-A10, without limitation.

Embodiment/Example B

A method comprising: receiving a fluid into an interior of a vibratableflow tube, wherein at least a portion of a surface of the interior isfunctionalized with a reactant sensitive to an analyte; vibrating theflow tube; detecting a frequency of the fluid received in the interiorof the flow tube during vibration thereof with a vibration detectorcoupled to the flow tube; and determining a frequency shift over time ofthe detected frequency with measurement circuitry coupled to thevibration detector, wherein the frequency shift corresponds to thepresence of the analyte, the analyte having reacted with the reactant.

Embodiment/Example B may have one or more of the following additionalelements in any combination:

Element B1: Wherein the flow tube is vibratable by a vibration sourcecoupled to the flow tube.

Element B2: Wherein the surface of the interior is functionalized with aplurality of reactants sensitive to a plurality of analytes, and aplurality of frequency shifts is determined where each frequency shiftcorresponds to a single analyte.

Element B3: Wherein the reactant is selected from the group consistingof gold, silver, copper, iron, nickel, a gold alloy, a silver alloy, acopper alloy, an iron alloy, a nickel alloy, a precious metal, a noblemetal, a precious metal alloy, a noble metal alloy, a solid chelatingagent, sulfur-limonene polysulfide, a piezoelectric crystal, a salt, afrangible material, an antibody, and any combination thereof.

Element B4: Wherein the functionalization of the surface of the interiorwith the reactant is selected from the group consisting of adhering thereactant to the surface of the interior, mechanically attaching thereactant to the surface of the interior, chemical deposition to thesurface of the interior, welding the reactant to the surface of theinterior, brazing the reactant to the surface of the interior, and anycombination thereof.

Element B5: Wherein the analyte is selected from the group consisting ofmercury, hydrogen sulfide, a salt, carbon dioxide, solid particulates,biological molecules, microorganisms, and any combination thereof.

Element B6: Wherein the vibration detector is selected from the groupconsisting of a metallic wire, a fiber optic, a strain gauge, and anycombination thereof.

Element B7: Wherein the frequency shift further corresponds to acharacteristic of the analyte, the characteristic selected from thegroup consisting of a mass of the analyte, a concentration of theanalyte, and any combination thereof.

Element B8: Wherein the sensor is located in a formation testing tool.

Element B9: Wherein the sensor is located in an oil fluid stream, a gasfluid stream, or an aqueous fluid stream at a surface location.

Element B10: Wherein the sensor is located in an oil fluid stream, a gasfluid stream, or an aqueous fluid stream at a downhole location in awellbore.

By way of non-limiting example, exemplary combinations applicable to Binclude: B1-B10; B4, B5, and B7; B3 and B10; B1, B4, B6, and B7; B8 andB10; and any other combination of any one or more of B1-B10, withoutlimitation.

Embodiment/Example C

A method comprising: detecting a first frequency of a fluid with a firstfrequency sensor comprising: a first vibratable flow tube having aninterior for receiving the fluid, wherein at least a portion of asurface of the interior is functionalized with a first reactantsensitive to a first analyte; and a first vibration detector coupled tothe first flow tube for detecting the frequency of the fluid received bythe first flow tube during vibration thereof; detecting a secondfrequency of the fluid with a second frequency sensor comprising: asecond vibratable flow tube having an interior for receiving the fluid;and a second vibration detector coupled to the second flow tube fordetecting the frequency of the fluid received by the second flow tubeduring vibration thereof; and determining a comparative shift over timebetween the detected first frequency and the detected second frequencywith measurement circuitry coupled to the first vibration detector andthe second vibration detector, wherein the comparative frequency shiftcorresponds to the presence of the first analyte, the first analytehaving reacted with the first reactant.

Embodiment/Example C may have one or more of the following additionalelements in any combination:

Element C1: Wherein at least a portion of a surface of the interior ofthe second flow tube is functionalized with a second reactant sensitiveto a second analyte, and further comprising detecting a first singleshift over time of the detected second frequency with the measurementcircuitry, wherein the first single frequency shift corresponds to thepresence of the second analyte, the second analyte having reacted withthe second reactant.

Element C2: Wherein the first flow tube is vibratable by a vibrationsource coupled to the first flow tube.

Element C3: Wherein the second flow tube is vibratable by a vibrationsource coupled to the second flow tube.

Element C4: Wherein the surface of the interior of the first flow tubeis functionalized with a plurality of reactants sensitive to a pluralityof analytes, and a plurality of frequency shifts is determined whereeach frequency shift corresponds to a single analyte.

Element C5: Wherein a surface of the interior of the second flow tube isfunctionalized with a plurality of second reactants sensitive to aplurality of second analytes, and a plurality of frequency shifts isdetermined where each frequency shift corresponds to a single secondanalyte.

Element C6: Wherein the first reactant is selected from the groupconsisting of gold, silver, copper, iron, nickel, a gold alloy, a silveralloy, a copper alloy, an iron alloy, a nickel alloy, a precious metal,a noble metal, a precious metal alloy, a noble metal alloy, a solidchelating agent, sulfur-limonene polysulfide, a piezoelectric crystal, asalt, a frangible material, an antibody, and any combination thereof.

Element C7: Wherein at least a portion of a surface of the interior ofthe second flow tube is functionalized with a second reactant sensitiveto a second analyte, and wherein the second reactant is selected fromthe group consisting of gold, silver, copper, iron, nickel, a goldalloy, a silver alloy, a copper alloy, an iron alloy, a nickel alloy, aprecious metal, a noble metal, a precious metal alloy, a noble metalalloy, a solid chelating agent, sulfur-limonene polysulfide, apiezoelectric crystal, a salt, a frangible material, an antibody, andany combination thereof.

Element C8: Wherein the functionalization of the surface of the interiorof the first flow tube with the first reactant is selected from thegroup consisting of adhering the first reactant to the surface of theinterior of the first flow tube, mechanically attaching the firstreactant to the surface of the interior of the first flow tube, chemicaldeposition to the surface of the interior of the first flow tube,welding the first reactant to the surface of the interior of the firstflow tube, brazing the first reactant to the surface of the interior ofthe first flow tube, and any combination thereof.

Element C9: Wherein at least a portion of a surface of the interior ofthe second flow tube is functionalized with a second reactant sensitiveto a second analyte, and wherein functionalization of the surface of theinterior of the second flow tube with the second reactant is selectedfrom the group consisting of adhering the second reactant to the surfaceof the interior of the second flow tube, mechanically attaching thesecond reactant to the surface of the interior of the second flow tube,chemical deposition to the surface of the interior of the second flowtube, welding the second reactant to the surface of the interior of thesecond flow tube, brazing the second reactant to the surface of theinterior of the second flow tube, and any combination thereof.

Element C10: Wherein the first analyte is selected from the groupconsisting of mercury, hydrogen sulfide, a salt, carbon dioxide, solidparticulates, biological molecules, microorganisms, and any combinationthereof.

Element C11: Wherein at least a portion of a surface of the interior ofthe second flow tube is functionalized with a second reactant sensitiveto a second analyte, and wherein the second analyte is selected from thegroup consisting of mercury, hydrogen sulfide, a salt, carbon dioxide,solid particulates, biological molecules, microorganisms, and anycombination thereof.

Element C12: Wherein a vibration detector selected from the groupconsisting of the first vibration detector, the second vibrationdetector, and any combination thereof is selected from the groupconsisting of a metallic wire, a fiber optic, a strain gauge, and anycombination thereof.

Element C13: Wherein a sensor selected from the group consisting of thefirst frequency sensor, the second frequency sensor, and any combinationthereof is located in a formation testing tool.

Element C14: Wherein a sensor selected from the group consisting of thefirst frequency sensor, the second frequency sensor, and any combinationthereof is located in an oil fluid stream, a gas fluid stream, or anaqueous fluid stream at a surface location.

Element C15: Wherein a sensor selected from the group consisting of thefirst frequency sensor, the second frequency sensor, and any combinationthereof is located in an oil fluid stream, a gas fluid stream, or anaqueous fluid stream at a downhole location in a wellbore.

By way of non-limiting example, exemplary combinations applicable to Cinclude: C1-C15; C1, C4, C11, and C15; C12 and C13; C2, C5, and C7; C8,C13, and C15; C14 and C15; C10, C12, and C14; and any other combinationof any one or more of C1-C15, without limitation.

Therefore, the embodiments disclosed herein are well adapted to attainthe ends and advantages mentioned as well as those that are inherenttherein. The particular embodiments disclosed above are illustrativeonly, as they may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularillustrative embodiments disclosed above may be altered, combined, ormodified and all such variations are considered within the scope andspirit of the present disclosure. The embodiments illustrativelydisclosed herein suitably may be practiced in the absence of any elementthat is not specifically disclosed herein and/or any optional elementdisclosed herein. While compositions and methods are described in termsof “comprising,” “containing,” or “including” various components orsteps, the compositions and methods can also “consist essentially of” or“consist of” the various components and steps. All numbers and rangesdisclosed above may vary by some amount. Whenever a numerical range witha lower limit and an upper limit is disclosed, any number and anyincluded range falling within the range is specifically disclosed. Inparticular, every range of values (of the form, “from about a to aboutb,” or, equivalently, “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to setforth every number and range encompassed within the broader range ofvalues. Also, the terms in the claims have their plain, ordinary meaningunless otherwise explicitly and clearly defined by the patentee.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the element that itintroduces.

What is claimed is:
 1. A frequency sensor comprising: a vibratable flowtube having an interior for receiving a fluid, wherein at least aportion of a surface of the interior is functionalized with a reactantsensitive to an analyte; a vibration detector coupled to the vibratableflow tube for detecting a frequency of the fluid received by thevibratable flow tube during vibration thereof; and measurement circuitrycoupled to the vibration detector for determining a frequency shift overtime of the detected frequency, wherein the frequency shift correspondsto the presence of the analyte, the analyte having reacted with thereactant.
 2. The frequency sensor of claim 1, wherein the vibratableflow tube is vibratable by a vibration source coupled to the vibratableflow tube.
 3. The frequency sensor of claim 1, wherein the surface ofthe interior is functionalized with a plurality of reactants sensitiveto a plurality of analytes, and a plurality of frequency shifts isdetermined where each frequency shift corresponds to a single analyte.4. The frequency sensor of claim 1, wherein the reactant is selectedfrom the group consisting of gold, silver, copper, iron, nickel, a goldalloy, a silver alloy, a copper alloy, an iron alloy, a nickel alloy, aprecious metal, a noble metal, a precious metal alloy, a noble metalalloy, a solid chelating agent, sulfur-limonene polysulfide, apiezoelectric crystal, a salt, a frangible material, an antibody, andany combination thereof.
 5. The frequency sensor of claim 1, wherein thefunctionalization of the surface of the interior with the reactant isselected from the group consisting of adhering the reactant to thesurface of the interior, mechanically attaching the reactant to thesurface of the interior, chemical deposition to the surface of theinterior, welding the reactant to the surface of the interior, brazingthe reactant to the surface of the interior, and any combinationthereof.
 6. The frequency sensor of claim 1, wherein the analyte isselected from the group consisting of mercury, hydrogen sulfide, a salt,carbon dioxide, solid particulates, biological molecules,microorganisms, and any combination thereof.
 7. The frequency sensor ofclaim 1, wherein the vibration detector is selected from the groupconsisting of a metallic wire, a fiber optic, a strain gauge, and anycombination thereof.
 8. The frequency sensor of claim 1, wherein thefrequency shift further corresponds to a characteristic of the analyte,the characteristic selected from the group consisting of a mass of theanalyte, a concentration of the analyte, and any combination thereof. 9.The frequency sensor of claim 1, wherein the frequency sensor is locatedin a formation testing tool.
 10. The frequency sensor of claim 1,wherein the frequency sensor is located in an oil fluid stream, a gasfluid stream, or an aqueous fluid stream at a surface location.
 11. Thefrequency sensor of claim 1, wherein the frequency sensor is located inan oil fluid stream, a gas fluid stream, or an aqueous fluid stream at adownhole location in a wellbore.
 12. A method comprising: receiving afluid into an interior of a vibratable flow tube, wherein at least aportion of a surface of the interior is functionalized with a reactantsensitive to an analyte; vibrating the vibratable flow tube; detecting afrequency of the fluid received in the interior of the vibratable flowtube during vibration thereof with a vibration detector coupled to thevibratable flow tube; and determining a frequency shift over time of thedetected frequency with measurement circuitry coupled to the vibrationdetector, wherein the frequency shift corresponds to the presence of theanalyte, the analyte having reacted with the reactant.
 13. The method ofclaim 12, wherein the vibratable flow tube is vibratable by a vibrationsource coupled to the vibratable flow tube.
 14. The method of claim 12,wherein the surface of the interior is functionalized with a pluralityof reactants sensitive to a plurality of analytes, and a plurality offrequency shifts is determined where each frequency shift corresponds toa single analyte.
 15. The method of claim 12, wherein the frequencyshift further corresponds to a characteristic of the analyte, thecharacteristic selected from the group consisting of a mass of theanalyte, a concentration of the analyte, and any combination thereof.16. The method of claim 12, wherein the vibratable flow tube is locatedin a formation testing tool.
 17. The method of claim 12, wherein thevibratable flow tube is located in an oil fluid stream, a gas fluidstream, or an aqueous fluid stream at a surface location.
 18. The methodof claim 12, wherein the vibratable flow tube is located in an oil fluidstream, a gas fluid stream, or an aqueous fluid stream at a downholelocation in a wellbore.
 19. A method comprising: detecting a firstfrequency of a fluid with a first frequency sensor comprising: a firstvibratable flow tube having an interior for receiving the fluid, whereinat least a portion of a surface of the interior is functionalized with afirst reactant sensitive to a first analyte; and a first vibrationdetector coupled to the first vibratable flow tube for detecting thefrequency of the fluid received by the first vibratable flow tube duringvibration thereof; detecting a second frequency of the fluid with asecond frequency sensor comprising: a second vibratable flow tube havingan interior for receiving the fluid; and a second vibration detectorcoupled to the second vibratable flow tube for detecting the frequencyof the fluid received by the second vibratable flow tube duringvibration thereof; and determining a comparative shift over time betweenthe detected first frequency and the detected second frequency withmeasurement circuitry coupled to the first vibration detector and thesecond vibration detector, wherein the comparative frequency shiftcorresponds to the presence of the first analyte, the first analytehaving reacted with the first reactant.
 20. The method of claim 19,wherein at least a portion of a surface of the interior of the secondvibratable flow tube is functionalized with a second reactant sensitiveto a second analyte, and further comprising detecting a first singleshift over time of the detected second frequency with the measurementcircuitry, wherein the first single frequency shift corresponds to thepresence of the second analyte, the second analyte having reacted withthe second reactant.